We will continue our studies of prolactin secretion in man. We are conducting experiments to clarify the factors which potentiate the neurogenic reflex initiated by suckling. We have evidence that this mechanism is easily inhibited by psychologic factors. We will continue to study regulation of GH and prolactin secretion by pituitary tumors. In particular we hope to define criteria for separation of physiologic and pathologic secretion of these hormones. This becomes of importance in establishing criteria for exploration for microadenomata of the pituitary. Investigations of isolated pituitary granules will continue to determine the nature of the matrix material and the process of granule formation. We will use a perifusion system to study the kinetics of response of rat and human pituitary tissues to various hypophysiotropic hormones and other agents.